Étienne-Louis Malus

Étienne-Louis Malus (/ˈɛtiɛn ˈluːi məˈluːs/; French: [malys]; 23 July 1775 – 24 February 1812) was a French officer, engineer, physicist, and mathematician.

Malus was born in Paris, France. He participated in Napoleon's expedition into Egypt (1798 to 1801) and was a member of the mathematics section of the Institut d'Égypte. Malus became a member of the Académie des Sciences in 1810. In 1810 the Royal Society of London awarded him the Rumford Medal.

His mathematical work was almost entirely concerned with the study of light. He studied geometric systems called ray systems, closely connected to Julius Plücker's line geometry. He conducted experiments to verify Christiaan Huygens's theories of light and rewrote the theory in analytical form. His discovery of the polarization of light by reflection was published in 1809 and his theory of double refraction of light in crystals, in 1810.

Malus attempted to identify the relationship between the polarising angle of reflection that he had discovered, and the refractive index of the reflecting material. While he deduced the correct relation for water, he was unable to do so for glasses due to the low quality of materials available to him (most glasses at that time showing a variation in refractive index between the surface and the interior of the glass). It was not until 1815 that Sir David Brewster was able to experiment with higher quality glasses and correctly formulate what is known as Brewster's law. This law was later explained theoretically by Augustin Fresnel, as a special case of his Fresnel equations.

Malus is probably best remembered for Malus's law, giving the resultant intensity, when a polariser is placed in the path of an incident beam. His name is one of the 72 names inscribed on the Eiffel tower.

Étienne-Louis Malus
Etienne-Louis Malus
Étienne-Louis Malus
Born23 July 1775
Died24 February 1812 (aged 36)
Known forPolarization of light
Malus's law
AwardsRumford Medal (1810)
Scientific career

Selected works


  • Kahr, Bart; Claborn, Kacey (2008), "The lives of Malus and his bicentennial law.", ChemPhysChem (published Jan 11, 2008), 9 (1), pp. 43–58, doi:10.1002/cphc.200700173, PMID 17680582

External links

1775 in science

The year 1775 in science and technology involved some significant events.

1812 in France

Events from the year 1812 in France

1812 in science

The year 1812 in science and technology involved some significant events, listed below.

Brewster's angle

Brewster's angle (also known as the polarization angle) is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized. This special angle of incidence is named after the Scottish physicist Sir David Brewster (1781–1868).

Corps of Bridges, Waters and Forests

The Corps des ponts, des eaux et des forêts (in English "Corps of Bridges, Waters and Forests") is a technical Grand Corps of the French State (grand corps de l'Etat). Its members are mainly employed by the French Ministry of Environment and Energy and by the Ministry of Agriculture. Most of them are from École polytechnique, where they are selected based on their ranking, and from École normale supérieure (Ulm) or the regular curriculum of the École des ponts ParisTech.

People entering the Corps (around 60 each year) are trained either at École des ponts ParisTech and AgroparisTech or abroad in specific fields, in particular when they are willing to pursue a PhD.

In 2002, the Corps des ponts et chaussées, and the different corps formed by the civil aviation engineers, the geography engineers and the meteorological engineers merged.

In 2009, the Corps des ponts et chaussées (in english "Corps of Bridges and Roads") and the Corps du génie rural, des eaux et des forêts (in english "Corps of Rural Engineering, Waters and Forests") merged into the current Corps des ponts, des eaux et des forêts.

Many executive positions in France's industries and administration are held by Corps des Ponts engineers. Being admitted to the Corps des Ponts program is still considered a significant fast-track for executive careers.

François Arago

Dominique François Jean Arago (Catalan: Domènec Francesc Joan Aragó), known simply as François Arago (French: [fʁɑ̃swa aʁaɡo]; Catalan: Francesc Aragó, IPA: [fɾənˈsɛsk əɾəˈɣo]; 26 February 1786 – 2 October 1853), was a French mathematician, physicist, astronomer, freemason, supporter of the carbonari and politician.

Index of physics articles (E)

The index of physics articles is split into multiple pages due to its size.

To navigate by individual letter use the table of contents below.

Jacques Frédéric Français

Jacques Frédéric Français (20 June 1775 – 9 March 1833) was a French engineer and mathematician.

Jacques Étienne Bérard

Jacques Etienne Bérard (12 October 1789 – 10 June 1869) was a French naturalist, chemist and physicist.

July 23

July 23 is the 204th day of the year (205th in leap years) in the Gregorian calendar. There are 161 days remaining until the end of the year.

List of the 72 names on the Eiffel Tower

On the Eiffel Tower, seventy-two names of French scientists, engineers, and mathematicians are engraved in recognition of their contributions. Gustave Eiffel chose this "invocation of science" because of his concern over the protests against the tower. The engravings are found on the sides of the tower under the first balcony, in letters about 60 cm high, and originally painted in gold.

The engraving was painted over at the beginning of the twentieth century and restored in 1986–1987 by Société Nouvelle d'exploitation de la Tour Eiffel, the company contracted by the city of Paris to operate the Tower. The repainting of 2010–2011 restored the letters to their original gold colour.

There are also names of the engineers who helped build the tower and design its architecture on the top of the tower on a plaque, where a laboratory was built as well.

List of École Polytechnique alumni

This is a list of notable people affiliated with the École Polytechnique. Alumni of the École Polytechnique are traditionally referred to as "X", or "Xnnnn", where nnnn stands for the year of admission into the school.

Malus (disambiguation)

Malus, the apples, is a genus of about 30–35 species of small deciduous trees or shrubs in the family Rosaceae, including most importantly the domesticated Orchard or Table Apple.

Malus may also refer to:

Bonus-Malus, a scheme of reward and punishment

Malus (constellation), an asterism that was part of the Argo Navis constellation

Étienne-Louis Malus (1775–1812), French officer, engineer, physicist, and mathematician

Malus (Castlevania), a young boy who is the reincarnation of Dracula in the video games Castlevania and Castlevania: Legacy of Darkness

Edward Malus, played by Nicolas Cage, the protagonist of The Wicker Man

Karl Malus, M.D., a fictional villain from Marvel Comics

The Malus, a monster appearing in the Doctor Who story "The Awakening"

The Malus, a playable race in the computer game O.R.B: Off-World Resource Base

Malus, the sixteenth and final Colossus in Shadow of the Colossus

Malus Code, a Japanese visual novel like game.

Malus Island

Malus Island is an island 8 kilometres (4.5 nmi) south of Cape Evensen, lying in Auvert Bay off the northwest coast of Stresher Peninsula, in Graham Land, Antarctica. It was charted by the British Graham Land Expedition under John Rymill, 1934–37, and was named by the UK Antarctic Place-Names Committee in 1960 for French physicist Étienne-Louis Malus, who discovered the polarization of light by reflection, a fact subsequently used in the design of snow goggles.

Plane of polarization

The term plane of polarization refers to the direction of polarization of linearly-polarized light or other electromagnetic radiation. Unfortunately the term is used with two contradictory meanings. As originally defined by Étienne-Louis Malus in 1811, the plane of polarization happened to coincide with the plane containing the direction of propagation and the magnetic vector; but this was not known at the time. In modern literature, the term plane of polarization, if it is used at all, more often refers to the plane containing the direction of propagation and the electric vector, because the electric field has the greater propensity to interact with matter. That propensity, together with Malus's definition and Fresnel's speculations on the luminiferous aether, led early investigators to define the "plane of vibration" as perpendicular to the plane of polarization and containing the direction of propagation.

This history must be taken into account when interpreting the term plane of polarization in existing literature. Sometimes the meaning can only be inferred from the context. In original writing, confusion can be avoided by specifying the orientation of a particular vector.


A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance.Some chemical substances are optically active, and polarized (uni-directional) light will rotate either to the left (counter-clockwise) or right (clockwise) when passed through these substances. The amount by which the light is rotated is known as the angle of rotation. The angle of rotation is basically known as observed angle.

Rumford Medal

Not to be confused with the Rumford Prize

The Rumford Medal is an award bestowed by Britain's Royal Society every alternating year for "an outstandingly important recent discovery in the field of thermal or optical properties of matter made by a scientist working in Europe".

First awarded during 1800, it was created after a 1796 donation of $5000 by the scientist Benjamin Thompson, known as Count Rumford, and is accompanied by a gift of £1000. Since its inception, the award has been granted to 101 scientists, including Rumford himself during 1800.

It has been awarded to citizens of the United Kingdom fifty-four times, Germany seventeen times, France fourteen times, the Netherlands seven times, Sweden four times, the United States three times, Italy twice and once each to citizens of Australia, Hungary, Belgium, Luxembourg and New Zealand.

Society of Arcueil

The Society of Arcueil was a circle of French scientists who met regularly on summer weekends between 1806 and 1822 at the country houses of Claude Louis Berthollet and Pierre Simon Laplace at Arcueil, then a village 3 miles south of Paris.

Timeline of electromagnetism and classical optics

Timeline of electromagnetism and classical optics lists, within the history of electromagnetism, the associated theories, technology, and events.

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